Because coronary atherosclerosis is nearly always a diffuse process among patients with symptomatic coronary heart disease (CAD), coronary angiograms in these patients often underestimate the degree of luminal narrowing because sites of maximal narrowing are compared to adjacent sites which also are narrowed but just less extensively. The finding of calcific deposit adjacent to contrast material in a coronary angiogram, however, is a clue that the luminagram does not indicate the original lumen and that the angiogram (or angiographer) is underestimating the actual amount of narrowing because the calcific deposits are virtually always within atherosclerotic plaques which are located within the intima.